The present invention relates to an electronic circuit component using a ceramic base. More particularly, it relates to an electrically conductive paste for circuit film, an electronic circuit component having a copper film circuit of 10 .mu.m or less in film thickness formed from said paste and a method for producing the electronic circuit component.
Copper circuit conductor of thick film hybrid IC has been produced by printing-firing of a conductive paste containing copper fine powder and frit glass (cf. Japanese Patent Kokai=Laid-Open=Sho 58-68803).
The above copper circuit film has the excellent characteristic, i.e., lower electric resistance than that of other metallic materials such as gold, but has the defect of difficulty in formation of fine circuit.
Etching method according to photo-lithography has been known for producing fine patterns. This method can provide considerably fine patterns, but this method also has some limits and the accuracy of etching depends on aspect ratio (normal critical value: 1/10) determined by film thickness/width of line of the wiring circuit film to be formed.
Considering the aspect ratio, circuit patterns can be made finer with decrease in thickness of circuit film, but practically it is not easy to form a circuit film of less than 15 .mu.m in thickness using a conductive paste.
The following methods can be considered for making a copper circuit film thinner.
One is to control the film thickness by using a paste conspicuously less in copper fine powder content than content of organic solvent or organic binder which is a vehicle or a paste comprising an organocopper compound. However, the formed copper film is reticulated due to coagulation and smooth film cannot be obtained with a film thickness of less than 15 .mu.m.
Another is to form a copper circuit film by chemical plating or by combination of chemical plating and electroplating. According to this method, optional film thickness can be easily obtained, but the film is low in adhesiveness to a ceramic base and is apt to peel off upon undergoing heat cycle.
Other methods are sputtering method and CVD method, but mass-production equipments for these methods are difficult to obtain and besides the film is also small in adhesion strength to ceramic base.